The present invention relates to a method and an apparatus for producing a molded resin product with a simulated wood grain pattern on an exterior surface thereof.
This application is based on Japanese Patent Application No. Hei 9-167706, the contents of which are incorporated herein by reference.
Molded resin products with simulated wood grain patterns, which are inexpensive and durable, have been substituted for natural wood in desks, furniture, walls, and floors in recent years. The molded resin products exhibit simulated wood grain patterns on their surface, which are achieved by forming layers with different colors.
A prior method for producing a molded resin product with simulated wood grain patterns comprises the steps of supplying a synthetic molten resin, which includes resins with different colors, into a mold cell, and solidifying the synthetic resin so as to achieve simulated wood grain patterns, as disclosed in U.S. Pat. No. 3,565,737 and JP-A-53090372.
However, the reproduced wood grain appearance of the molded resin product of the prior method may often be degraded because it depends on the condition of the mixture of the resins. A real wood grain appearance cannot be easily achieved because the patterns are stripes with different colors and widths positioned at irregular intervals.
It is therefore an object of the present invention to provide a method and an apparatus for manufacturing a molded resin product with wood grain patterns, the method easily producing molded resin products which are almost identical replicas of genuine wood and have grain patterns of different colors and widths positioned at irregular intervals.
In order to accomplish the above object, a method for producing a molded resin product with a simulated wood grain pattern on an exterior surface thereof, comprises the steps of: supplying a first molten resin into a mold cell to form a resin layer which forms the exterior surface; making a plurality of grooves through the resin layer so as to reach the exterior surface before the molten resin solidifies; filling up the grooves with a second molten resin such that the exterior surface exhibits simulated wood grain patterns; and solidifying the first resin and the second resin. The grains patterns showing a real wood appearance can be easily reproduced since the grooves are formed through the resin layer and the second molten resin is thereafter supplied into the grooves.
In another aspect of the present invention, a method for producing a molded resin product with a simulated wood grain pattern on an exterior surface thereof comprises the steps of: supplying a plurality of kinds of molten resin into a mold cell to form a plurality of resin layers, the lowest resin layer forming the exterior surface; making a plurality of grooves through the lowest resin layer to the exterior surface so as to fill up the grooves with the molten resin of an upper resin layer before the molten resin solidifies such that the exterior surface exhibits simulated wood grain patterns; and solidifying the resin layers. The grain patterns having a real wood appearance can be easily reproduced since a plurality of resin layers within the mold cell are formed and the grooves through the lowest resin layer are made so that the upper resin layer partly sinks into the grooves before the layers have solidified.
The grooves are preferably different in width, and the grooves are preferably provided at irregular intervals. The most natural wood grain patterns can be achieved because the grain patterns on the exterior surface are different in width and are positioned at irregular intervals due to the grooves having different widths and being positioned at irregular intervals.
A plurality of rods may be moved through the resin layer to make the grooves, thereby facilitating the manufacturing process of the wood-like molded resin product and enhancing the wood-like appearance. The exterior surface may be preferably arranged on the bottom of the cell, and the rods may be moved while in contact with the inside bottom of the mold cell.
In another aspect of the present invention, an apparatus for producing a molded resin product with a simulated wood grain pattern on the exterior surface thereof comprises: a mold cell having an inside surface on which an exterior surface of the molded resin product is disposed; a supply means for supplying molten resin into the mold cell; and a groove-forming means for forming a plurality of grooves through a resin layer within the mold cell, the groove-forming means having a plurality of rods which are movable while maintaining contact the inside surface of the mold cell. The grain patterns having a real wood appearance can be easily produced since a molten resin having a different color is supplied into the grooves of the resin layer to form wood-like grains on the surface in contact with the mold cell.
The rods are preferably different in width, and the rods are preferably provided at irregular intervals. The most natural wood grain patterns can be achieved because the grain patterns on the exterior surface are different in width and are positioned at irregular intervals due to the grooves having different widths and being positioned at irregular intervals. The inside surface may be disposed on the bottom in the mold cell.